By Jeremy Ross

CHICAGO (CBS)– Cloated in an eerie silence the day after three people were fatally shot at the hands of a doctor’s ex-fiance, the Mercy Hospital emergency room is a different place now that Dr. Tamara O’Neal will never walk through the doors again.

According to the National Coalition Against Domestic Violence, 20 people experience physical violence at the hands of their partner every minute in the U.S.

Intimate Partner Violence, described by Centers for Disease Control and Prevention as a public health problem that affects millions of Americans, is considered physical, sexual or psychological harm by a partner. This type of violence accounts for 15 percent of violent crime.

Statistics show that an average of every one in three female murder victims is killed by their intimate partner—former or current.

That was the case for 38-year-old Dr. Tamara O’Neal, who was killed by her ex-fiance Juan Lopez Monday at Mercy Hospital, where she worked as an E.R. doctor. The former couple had only recently ended their engagement.

Dr. Tamara O’Neal was fatally shot by her ex-fiance as she was walking to work at Mercy Hospital.

Lopez showed up with a gun and shot O’Neal in the hospital parking lot. He was said to have had a history with guns.

Amanda Pyron is the executive director of the Chicago Metropolitan Battered Women’s Network and says Monday’s tragedy is far too similar to countless others.

Experts say women in abusive relationships are 500 percent more likely to die if there’s a gun present in a relationship.

At only 38, Dr. O’Neal had a promising future ahead of her until she became a victim of domestic violence Monday.

Friends and colleagues gathered at a vigil Tuesday to tearfully remember O’Neal and talk about whether there were warning signs.

The Battered Women’s Network estimates 20 percent of people killed in domestic disputes involving a firearm are bystanders.